Question

Query tuning problem

Asked by: chedgey

I have recently upgraded a third party application from Oracle 8.1.6 to Oracle 9.2.0.7.0 and all is well apart from a couple of queries that are running poorly. The queries are based on a simple view and I am having problems seeing why the cost based optimiser is behaving as it is with it.

When i run the uderlying query of the view as a SQL statement it gives me a high cost but if I strip out the column list (keeping the rest of the query consitent) it behaves much better. Here are the plans from the 2 versions of the query:

Original Query
----------------
Explain Plan
Set STATEMENT_ID='GJC3'
For
SELECT IF_.R_OBJECT_ID,IF_.OBJECT_NAME
      ,IF_.R_OBJECT_TYPE,IF_.TITLE
      ,IF_.SUBJECT,IF_.A_APPLICATION_TYPE
      ,IF_.A_STATUS,IF_.R_CREATION_DATE,IF_.R_MODIFY_DATE,IF_.R_MODIFIER
      ,IF_.R_ACCESS_DATE,IF_.A_IS_HIDDEN,IF_.I_IS_DELETED,IF_.A_RETENTION_DATE
      ,IF_.A_ARCHIVE,IF_.A_COMPOUND_ARCHITECTURE,IF_.A_LINK_RESOLVED,IF_.I_REFERENCE_CNT
      ,IF_.I_HAS_FOLDER,IF_.R_LINK_CNT,IF_.R_LINK_HIGH_CNT,IF_.R_ASSEMBLED_FROM_ID
      ,IF_.R_FRZN_ASSEMBLY_CNT,IF_.R_HAS_FRZN_ASSEMBLY,IF_.I_CONTENTS_ID,IF_.A_CONTENT_TYPE,IF_.R_PAGE_CNT
      ,IF_.R_CONTENT_SIZE,IF_.A_FULL_TEXT,IF_.A_STORAGE_TYPE,IF_.I_CABINET_ID
      ,IF_.OWNER_NAME,IF_.OWNER_PERMIT,IF_.GROUP_NAME,IF_.GROUP_PERMIT,IF_.WORLD_PERMIT,IF_.I_ANTECEDENT_ID,IF_.I_CHRONICLE_ID,IF_.I_LATEST_FLAG,IF_.R_LOCK_OWNER,IF_.R_LOCK_DATE,IF_.R_LOCK_MACHINE,IF_.LOG_ENTRY,IF_.I_BRANCH_CNT,IF_.I_DIRECT_DSC,IF_.R_IMMUTABLE_FLAG,IF_.R_FROZEN_FLAG,IF_.R_HAS_EVENTS,IF_.ACL_DOMAIN,IF_.ACL_NAME,IF_.A_SPECIAL_APP,IF_.DOCUMENT_NUMBER,IF_.DOCUMENT_DATE,IF_.ISSUE_LEVEL
      ,IF_.I_IS_REFERENCE
      ,IF_.RESOLUTION_LABEL
      ,IF_.R_IS_VIRTUAL_DOC
      ,IF_.R_IS_PUBLIC
      ,IF_.R_CREATOR_NAME
      ,IF_.R_POLICY_ID
      ,IF_.R_RESUME_STATE
      ,IF_.R_CURRENT_STATE
      ,IF_.R_ALIAS_SET_ID
      ,IF_.I_IS_REPLICA
      ,IF_.A_CATEGORY
      ,IF_.LANGUAGE_CODE
      ,IF_.I_VSTAMP
      ,UY_.DCA_IDENTIFIER
      ,UY_.DCA_CURRENT_STATUS
      ,UY_.DCA_PROJECT
      ,UY_.DCA_DATE_OPENED
      ,UY_.DCA_DESCRIPTION
      ,UY_.DCA_FORMAL
      ,UY_.DCA_WORKFLOW_ID
      ,UY_.DCA_SUBMITTED
      ,UY_.DCA_DESTINATION
      ,UY_.DCA_PUBLISHING_INFO
      ,UY_.DCA_LOCKOWNER
      ,UY_.DCA_REJECTION_NOTES
      ,UY_.DCA_FINALISED_DATE
      ,UY_.DCA_FORMAL_START_DATE
      ,UY_.ACTIVE_REVIEWERS
  FROM LMREDMS.dm_sysobject_s IF_
      ,LMREDMS.lm_dca_s UY_
 WHERE IF_.R_OBJECT_ID=UY_.R_OBJECT_ID
/

Query Plan                                                                      
--------------------------------------------------------------------------------
1.33774 SELECT STATEMENT    GJC3 Cost=33774                                    
--2.1 HASH JOIN                                                                
  --3.1 TABLE ACCESS FULL LM_DCA_S                                              
  --3.2 TABLE ACCESS FULL DM_SYSOBJECT_S                                        


Column list removed
-----------------------
Explain Plan
Set STATEMENT_ID='GJC3'
For
SELECT IF_.R_OBJECT_ID
      ,UY_.R_OBJECT_ID
  FROM LMREDMS.dm_sysobject_s IF_
      ,LMREDMS.lm_dca_s UY_
 WHERE IF_.R_OBJECT_ID=UY_.R_OBJECT_ID
/
Query Plan                                                                      
--------------------------------------------------------------------------------
1.289 SELECT STATEMENT    GJC3 Cost=289                                        
--2.1 NESTED LOOPS                                                              
  --3.1 INDEX FAST FULL SCAN D_1F004421800001A1 UNIQUE                          
  --3.2 INDEX UNIQUE SCAN D_1F00442180000108 UNIQUE                            


Can anyone tell me why the first query with all the columns listed takes so much longer than the second. All tables are analyzed and the optimizer rule is set to "Choose. The DM_SYSOBJECTS_S table contains about 1,600,000 rows and the LM_DCA_S table about 33,000. Both tables have an index on the R_OBJECT_ID column

Thanks in advance

Chedgey

This Question has been solved and asker verified All Experts Exchange premium technology solutions are available to subscription members.

Subscribe now for full access to Experts Exchange and get

Instant Access to this Solution

  • Plus...
  • 30 Day FREE access, no risk, no obligation
  • Collaborate with the world's top tech experts
  • Unlimited access to our exclusive solution database
  • Never be left without tech help again

Subscribe Now

Asked On
2006-09-18 at 03:44:27ID21993058
Tags

query

Topic

Oracle Database

Participating Experts
2
Points
125
Comments
3

Trusted by hundreds of thousands everyday for fast, accurate and reliable tech support.

  • "The time we save is the biggest benefit of Experts Exchange to Warner Bros. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange." Mike Kapnisakis, Warner Bros.
  • "Our team likes having a resource that is more secure than just using Google and most experts using this service really know their stuff. It's nice to look here first versus using Google." Dayna Sellner, Lockheed Martin
  • "Anytime that I've been stumped with a problem, 9 out of 10 times Experts Exchange has either the accepted solution or an open discussion of the potential solution to the problem." Kenny Red, eBay Inc.

See what Experts Exchange can do for you.

Got a question?

We've got the answer.

Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.

Screenshot of Experts Exchange Knowledgebase

Need individual assistance?

Our experts are ready to help.

If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.

Screenshot of Experts Exchange Knowledgebase

Want to learn from the best?

Read articles from industry experts.

Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.

Screenshot of an Article

Working on a long term project?

Store your work and research.

Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.

Screenshot of Experts Exchange Knowledgebase

Access the answers to your technology questions today.

Subscribe Now

30-day free trial. Register in 60 seconds.

What Makes Experts Exchange Unique?

Members of the expert community talk about why the experience at Experts Exchange is different than what you will find anywhere else.

Trusted by the world's most respected brands.

image of each brand's logo

Faithfully serving IT professionals since 1996.

Experts Exchange Logo

Try it out and discover for yourself.

Subscribe Now

30-day free trial. Register in 60 seconds.

Related Solutions

  1. Oracle Tuning
    How do i tune an oracle database(7.3.4) for optimal performance?
  2. TUNING
    1) When we queried V$SQL and V$SQLAREA, we trapped EXECUTIONS, DISK_READS, BUFFER_GETS, FIRST_LOAD_TIME and SQL_TEXT. 2) What we found was for some SQL statements, the EXECUTIONS, DISK_READS and BUFFER_GETS were having very high values and for some very low values. 3) The 3 ...
  3. Tuning
    hai gays, i attended an interview. they asked so many ques i will post one by one. we will discuss and collect all our friends views 1. if a user called in phone and said the quey response is very poor, what u will do imme? 2. when u asked u to tune the database where u w...
  4. Sql Tuning
    Hi there. I have following query which consumes high IO and needs to bu tuned. Currently it works in 40 sec. And need to get 10 sec. SELECT SUM(A.TUTAR) FROM MHSFISL0_YTL A, KSAVEZN0 B WHERE A.SIRKOD=1 AND A.SIRKOD=B.SIRKOD AND B.YIL='2006' AND B.VEZNENO=1602 AND A.M...
  5. ORACLE TUNING
    WE HAVE AN APP USING ORACLE 9 WHICH HAS BEEN RUNNING FOR 3/4 YEARS FINE NOW USERS ARE EXPERIENCING SLOW RESPONSES INTERMITTENTLY WE THINK EITHER ORACLE DATABASE NEEDS TO RUN SOME TUNING PROGRAM "COMPUTE STATISTICS??" AS NOW DATA HAS EXPANDED TO A POINT TO MAKE ORAC...
  6. Tuning Oracle SQL Queries
    I have a SQL inside oracle package (version 8i) that takes more time to complete, the query has 2 tables to compare and it is like this select col A from TableA where customer = p_customer minus select ColB from TableB B where process_month in (select max(process_month) from...

Free Tech Articles

  1. WARNING: 5 Reasons why you should NEVER fix a computer for free.
    It is in our nature to love the puzzle. We are obsessed. The lot of us. We love puzzles. We love the challenge. We thrive on finding the answer. We hate disarray. It bothers us deep in our soul. W...
  2. SCCM OSD Basic troubleshooting
    SCCM 2007 OSD is a fantastic way to deploy operating systems, however, like most things SCCM issues can sometimes be difficult to resolve due to the sheer volume of logs to sift through and the dispe...
  3. Migrate Small Business Server 2003 to Exchange 2010 and Windows 2008 R2
    This guide is intended to provide step by step instructions on how to migrate from Small Business Server 2003 to Windows 2008 R2 with Exchange 2010. For this migration to work you will need the fo...
  4. Create a Win7 Gadget
    This article shows you how to create a simple "Gadget" -- a sort of mini-application supported by Windows 7 and Vista. Gadgets can be dropped anywhere on the desktop to provide instant information, ...
  5. Outlook continually prompting for username and password
    There have been a lot of questions recently regarding Outlook prompting for a username and password whilst using Exchange 2007. There are a few reasons why this would happen and I will try to cover t...
  6. Backup Exchange 2010 Information Store using Windows Backup
    There seems to be quite a lot of confusion around the ability to backup Exchange 2010 using the built in Windows Backup feature. This stems from the omission of this feature prior to Exchange 2007 s...

Cloud Class Webinars

  1. Avoiding Bugs in Microsoft Access
    Alison Balter takes and in-depth look at avoiding bugs in Access. In this webinar you will learn about using the immediate window to debug your applications, invoking the debugger, using breakpoints to troubleshoot, stepping through code, setting the next statement to execute, ...
  2. Top 10 Best New Features in Visio 2010
    Scott Helmers gives live demonstrations of the top 10 new features in Visio 2010. This webinar will teach you how to create compelling diagrams by adding shapes to the page with a single click, linking the shapes in a diagram to data in Excel (or SQL Server, or SharePoint), ...
  3. IT Consultant Business Secrets Revealed
    Michael Munger, Experts Exchange tech pro and IT consultant, pulls back the curtain on his very successful businesses and answers question on every IT consultant and business owner should know about. He shares secrets on what he did to solve the 5 most common problems in IT, ...
  4. Disaster Recovery and Business Continuity
    Quest CTO, Mike Billon, gives an overview of the steps involved in building a dunamic disaster recovery plan. Through case studies and an examination of software/hardware tooles for monitoring and testing, you'll gain a better understandin of where you are, where you want ...
  5. Organize Your Visio Diagrams with Containers and Lists
    Scott Helmers uses cross functional flowcharts, wireframe diagrams, data graphic legends and seating charts to teach you: how to ustilize all three new structured diagram components in Visio 2010, the best practices for organizeing shapes in previous version of Visio, how to organize ...
  6. How to Us Objects, Properties, Events and Methods in Microsoft Access
    Alison Dalter gives an in-depbth look at objects, properties, events and methods in Microsoft Access. In this webinar you will learn about using the object browser, referring to objects, working with properties and methods, working with object variables, understanding the ...

Join the Community

Give a Little. Get a Lot.

Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.

Join the Community

Answers

 

by: MohanKNairPosted on 2006-09-18 at 04:48:39ID: 17542534

The columns IF_.R_OBJECT_ID and  UY_.R_OBJECT_ID are available in the index itself, so no table access required. When there are other columns, table access is required. The query is making use of HASH JOIN.

NESTED LOOPS can be used only if there are indexes available for either IF_.R_OBJECT_ID or  UY_.R_OBJECT_ID

 

by: johnsonePosted on 2006-09-18 at 06:57:42ID: 17543519

Here is my guess.

The first query is selecting so many columns that the optimizer has determined that using the index would be inefficient.

The second query can be completely satisfied using only the indexes, so index scans are used.  You will see no table access in the plan for that query.



Try changing your optimizer mode (for the session) to FIRST_ROWS instead of CHOOSE.  CHOOSE tends to act like ALL_ROWS which will favor full table scans and hash joins, while FIRST_ROWS tends toward nested loops.

 

by: chedgeyPosted on 2006-09-21 at 06:57:13ID: 17569115

Thanks. Fixed the problem with an INDEX hint that took the execution time down from 65s to 0.01s.

Regards

chedgey

20120131-EE-VQP-002

3 Ways to Join

30-Day Free Trial

The Experts

98% positive feedback on 31,087 answers since March 2000. angeliii is a Microsoft Most Valuable Professional for his work with MS SQL Server & Develoment.

He has also proven his knowledge of Visual Basic Programming, PHP Scripting and Oracle Databases.

The Experts

97% positive feedback on 10,752 answers since July 2000. lrmoore has more than 18 years experience in the networking industry.

The six-time Mircosoft MVPs specialties include firewalls, virtual private networking, and network management.

Testimonials

"...and excellent source for support... Kind of like having your very own IT dept." Electriciansnet

Testimonials

"I was apprehensive at signing up at first. However... it has already made my life as an IT administrator much easier." JaCrews

Testimonials

"WOW! You guys have great, active, and knowledgeable people on here." moore50

Business Clients

Business Clients

In the Press

"If you’ve got a question... Experts Exchange can supply an answer.”

In the Press

"...an invaluable aid for both IT professionals and those who require tech support."

In the Press

"where IT professionals provide quick answers on just about any topic"

Business Account Plans

Loading Advertisement...